While the broad concept of separating food soils from the wash and rinse waters of dishwashing machines is abundantly old, as exemplified by U.S. Pat. No. 1,971,588, in recent years there has been renewed interest in this concept. By collecting food soil particles during the washing and rinsing operations of a dishwasher cycle, as they are removed from the tableware, redeposition of these particles on the tableware being cleaned is minimized. The net result of this action is earlier removal of the soil from the tableware, thus allowing the tableware to be cleaned with fewer water changes. If the number of water changes is not reduced, a higher degree of cleaniness is achieved.
Many approaches have been taken by prior art workers. Soil separation primarily by centrifugal action is relied upon in the teachings of the above noted U.S. Pat. No. 1,971,588. Prior art workers have also tried various types of screens and filter means through which the wash and rinse waters pass. It has been found, however, that particles of starchy foods and fibrous foods tend to stick to screens and filters, clogging them, and requiring the operator to remove and manually clean them frequently. An exemplary system using filters or screens is taught in U.S. Pat. No. 3,989,054. Sometimes special water jets or the like are employed to clean the screens, as is taught, for example, in U.S. Pat. No. 4,392,891.
It has been found that in order for a food soil separator to be beneficial to the operator, it must be of such configuration that the sticky soils are thoroughly removed automatically, and without any special attention or manipulative steps by the operator. Prior art workers, therefore, directed their attention away from screens and filters to other types of devices for separating the food soils. One such device is the sedimentation or separation chamber. According to this approach, a portion of the washing fluid or rinsing fluid is directed into a chamber and allowed to circulate therethrough at a low enough velocity to allow the particulate food soil to precipitate before the supernatant fluid is returned to the washing chamber. The use of such a chamber has a number of advantages. First of all, the passages are necessarily large and there are no screens to clog. In addition, the collected food soil can easily and thoroughly be disposed of directly to the drain when the dishwashing machine cycle advances to the drain operation. U.S. Pat. Nos. 4,150,680; 4,168,715 and 4,243,431 are exemplary of prior art soil separating apparatus utilizing both centrifugal separation and a soil separation chamber. The structures of these references utilize uni-directional pump motors causing the cleansed wash and rinse waters to be recirculated in the dishwasher chamber or vat. During the drain operation of the dishwasher cycle, collected soils from the chamber exit to the drain through an openable and closable valve means.
U.S. Pat. No. 4,319,599 teaches a soil separator utilizing both centrifugal force and a soil separating chamber. The apparatus of this patent employs a reversible motor which operates both a recirculation impeller and a drain pump impeller. The reference device also employs an annular wall means forming a guide chamber in fluid communication with the recirculating pump chamber and the separation chamber. The separation chamber is provided with a pressure-actuated valve which opens during the drain operation of the dishwasher cycle.
The present invention is directed to apparatus for removing food soil from the wash and rinse waters of an automatic dishwasher, of the type employing a separation chamber. The apparatus of the present invention is highly effective and fully automatic, requiring no special attention or manipulation by the operator. Unlike prior art structures, the apparatus of the present invention is characterized by an unique simplicity of design and operation. The device employs a bi-directional motor. The separation chamber contains at least one valve in the form of a simple check valve operated by the dishwasher fluid, itself.